Development of photographic images.



STATES PATENT OFFICE.

WILLIAM nay CALDWELL, or courier or INVERNES'S, SCOTLAND.

DEVELOPMENT OF PHOTOGRAPHIC IMAGES.

1,082,622. HoDrawing.

To all whom it may concern:

Be 't known that I, IVILLIAM HAY CALD- WELL, a. subject of the King ofGreat Britain and Ireland, residing in Invernessshire,Scotland,haveinvented Improvements in or -Relating to the Development ofPhotographic' Images, of which the following is a specification.

In the development of exposed silver haloid films there are three mainfactors to beta-ken into consideration, namely (a) the amount of' thesilverhaloid in the filmthat has, been afi'ected by light, that isto saythe number of unit portions of the haloid that havebeen affected; (1))the amount and nature of the'reducerpresent in the developer and (c) theamount of silver haloid solventpresent in the developer:

With all ordinary developers for bromid fast plates, the reducer issuchthat all-dissolved silver bromid present in iIistanta-neously reduced tosilver in contact with altered silver salt produced bv exposure tolightwith the result that the: whole of thelight affected unit portions ofsilver haloid :on each grain of the silver haloid present in the film.are not utilizedin bringing about the reduction of the whole grain, oneunit alone being sufficient to bring about the reduction of the wholegrain so that the image isnot developed in the most perfect mannerdesirable, especially in the case of With such developers, therefore,the efi'ect'ive workin units are the light affected aggregates of sllverhaloid', and since the effective working units are,

compared to the number of molecules present, few in number, the latitudeof the plate, as regards exposure, is small. This action is independentof the changes due to exposure in the film as is shown by the fact thatthe films forming the subject matter of former Letters Patent granted tome No. 956,567 dated May'3, 1910, though incapable of injury throughbeing over exposed, yet, with ordinary, developers, cannot be deavelopedto the same scale of gradations wlth different exposures.

Now the present invention has for its object to develop exposedphotographic films with a developer such that the silver haloid,

. TQ -JeXampIe siIVer bromid, dissolved by the developen-shall notbereduced so quickly as f'ordinary'developerbut shall, on theSpecification of Letters Patent.

Patented Dec. 30, 1913.

Application filed June 19, 1912. Serial No'. 704,623.

portions of silver haloid that havebeen af-' fected by light so thatsilver *haloid in solution shall be reduced to silver in contact witheach of'the unit portions, whereby a perfect developmentofthe'phot'ographic image can be obtained in the case of films that havehad along exposure. For thispurpose I have found that verysatisfactoryresults can be obtained by developing an exposed film with a solution ofa double salt obtained by combining an aromatic hydrazin base and analkali metal'sulfite, or by using. though not with such good results,the sulfurous acid salt of the base itself. v By these means, the properfunction of a perfect developer is fulfilled, namely that the developershould.

C H NH NH,NaHSO In all casesit is essential that the solution be acid tolitmus. any alkaline salt, 0. 9., na so is suflicient to destroy therequired propertyof the developer; The developer can also be preparedin-the' form of a dry white powder by mixing'the hydrazin base withsodium bisulfite in equal molecular proportions and adding thereto Waterin the proportion of 3% molecules.

- In practice it is found that phenyl hy- Even a slight excess of drazinis irritating to the hands of the op erator. By replacing one or mo ofthe atoms of hydrogen in the para or ortho position in the phenylnucleus with one or another of numerous available groups or certainelements this disadvantage is found to be overcome. Among suitableinorganic elements or groups may be mentioned chlorin, bromin or HSO,each possessing positive properties, or NH possessing negativeproperties while a large number of organic groups or radicals as forinstance hydro.- carbon radicals such as methyl (0H,),ethyl- (C 11 andso on are suitable. Substances of this character are included in thegeneric substitution bodies referred to in certain of the claims underthe expression anti-corrosive.

By the use of a developer such as described the silver salt in the filmis dissolved, transferred across the gelatin or like medium constitutingthe [ilm and deposited on the whole of the separate light affected unitspresent. the amount of silver reduced and deposited, and hence thedensity or the image obtained being limited only by the amount of silverpresent in the film. On the other hand, in the case of an ordinarydeveloper, the amount of silver deposited is limited by the ambunt or"silver reducedby a given exposure and is dependent upon the number ofgrains of silver haloid affected.

By regulating the strength of the new developer by using more or lesswater, any desired gradation of the developed image can be obtained bywell known laws, because, by altering the quantity of the solvent of theunaltered silver salts, one can vary the rate of solution compared tothat of diffusion in the film. Thus, one can starve the high lights andproduce a flat result by using more water and vice versa. Furthercontrol c anbe obtained by varying the temperature of the developerbefore use, as this changes the activity of the reducer in thedeveloper.

A suitable stock developing solution can be prepared by dissolving oneounce of the new developer in the state in thirty three ounces of waterat a temperature of allowing the solution to.

120 to 150 1?, cool and filtering it. For developing a film havingan-over-exposure of '10 to 100 times that technically called. correct, asuitable developer can be made by mixing two parts of the stock solutionwith one part of water and using the resulting developer at from 70 F.to F., the average time of development being from 20 to 45 minutes. .Forde veloping a film having an exposure of from 100 to 1000 times, thestock solution can be used without further.dilution, at a temperature offrom 60 F., to 50 F., the rule being the longer the exposure the coldershould be the developer. This rate will apply also to abnormal overexposures of say 5000 times and upward, where the temperature of thedevelopermay be lowered to 35 F. These extreme over exposures can bedevelopedat a higher temperature by the addition of solution to thedeveloper solution. I

' The films before development may advan tageously be immersed in a 2%solution of sodium carbonate anhydrous)'for about two minutes, theu inwater and the suriacewiped with a pad of cotton wool;

The present invention can advantageously beapplied inthe development ofimages on photographic films or surfaces-ofthe kind forming the subjectmatter of my said vformer Letters Patent No. 956567. With these films,any exposure however prolonged, up

to complete printing out, can be develr oped to give the correct scaleof density.

What I claim is 1. The herein described improvement in the art ofdeveloping a photographic film containing a silver salt, which consistsin subjecting the film to a slowly acting developer, acid to litmus,dissolving out thereby silver salt that has been .unacted upon by lightandvcausing the dissolved silver salt'to slowly diifuse or travelthrough the film medium to all the unit portionsot' the silver salt thathave been affected by light 'so that silver salt in solution shall bereduced to silver in contact with each of said unit portionssubstantially as described for the purpose set forth.

2. The herein described improvement in.- the art of developing aphotographic ,iilm containing a silver salt, which consists insubjecting the film to the action of a solution, acid to litmus,obtained by combining an aromatic hydrazin base with a compoundcontaining sulturous acid.

3 The herein described improvement in the art of developing aphotographic film containing a silver salt, which consists in subjectingthe film to the action of'a solution, acid to litmus, of a double saltobtained by combining an aromatic hydrazin base. and an alkali metalsulfite.

4. The herein described improvement in the art of developing aphotographic film containing a silver salt, which consists insubjectingthe film to the action of a solution, acid to litmus, of adouble salt obtained by combining an aromatic hydrazin base and acidsulfite of sodlum.

5. The herein described improvement in the art of developing aphotographic. film containing a silver salt, which consists insubjecting the film to the'action of a solution, acid to litmus, of adouble salt obtained by combining a phenyl hydrazin base and an alkalimetal'sulfite.

'6. The herein described improvement in the art-of developing aphotographic film containing a silver salt, Whichconsists in subjectingthe vfilm to the action'of a solution, acid to litmus, of a double saltobtained by combining a phenyl hydrazin base in which an atom ofhydrogen in the phenyl nucleus distant an odd number of positions fromthe hydrazinhas been replaced by an anti-corrosive substance, with analkali metal sulfi te, substantially as described.

7. The herein described improvement in the art of developing aphotographic film containing a silver salt, which consists in subjectingthe film to the action of a solu-.

tion, acid to litmus,-of a double salt obtain ed which an atom ofhydrogen in the phenyl nucleus has been replaced bya halogen, with analkali metal sulfite.

8. The herein described improvement in the art of developing aphotographic film containing .a silver salt, which consists insubjecting the film to the action of a solu-] tion, acid to litmus, of'a double salt obtained I by combining a phenyl hydrazin base in whichan atom of hydrogen in the ortho' position in the phenyl nucleus hasbeen-replaced by an anti-corrosive substance, with an alkali metalsulfite.

9. The herein described improvementint'h art ofdeveloping a photographicfilm' containing 'a'silver salt, .which consists in.

subjecting the fil-mto the action of a solution, acid to litmus, of adouble salt obtained" by combining a phenyl hydrazin base in which anatom of hydrogen in the phenyl nucleus distant an odd number ofpositions 'from the hydrazin has been replaced by bromin,'with an alkalimetal sulfite.

10. The herein described improvement in the art of developing aphotographic film containing a silver salt, which consists in subjectingthe film to the action of a solutiomacid to litmus, ofa double saltobtained by combining ortho-brom-phenyl-hydrazin.

with an alkali metal sulfite' 1 1.The herein described improvement inthe art of developing a photographic film" containing. a silver salt,which consists in.

subjecting the film to the action 'of a solution, acid to litmus, of adouble salt obtained by combining ortho-brozn-phenyl'hydrazin' with acidsulfite of sodium.

12. For developing photographic ,films containing afsilver salt,adeveloper comf prising an aromatic hydrazin base and an .acidsulfite'of an alkali metal. V

13. Forvdevelo-ping photogra hic films containing. a silver salt, a deveoper corn prisingla phenyl hydrazin base in which an atom of hydrogen inthe phenyl nucleus at distant an odd number of positions from, hydrazin,-has been replaced by an ant "corrosive substance, and an acid sulfiteof an alkali inetal.

1-4. For developing photographic films containing a silver salt, adeveloper com-' prising ortho-brom-pheny1 hydrazin and an acid sulfiteof an alkali metal. 15. For developing photographic films containing asilver .salt, -a liquidd'eveloper comprising an aqueous solution, acid.to litmus, ofa hydrazin base and an acidsulfite ofan alkali metal inequal molecular proportionsp' .16. For developing photographic filmscontaining 'a sil'ver salt a solution comprising .a substitutionproduct,-'in the phenyl nucleus, of phenyl 'hydrazin, said solutionbeing acid

